/*
*    Qizx/open 3.0 beta
*
* This code is the open-source version of Qizx.
* Copyright (C) 2004-2009 Axyana Software -- All rights reserved.
*
* The contents of this file are subject to the Mozilla Public License 
*  Version 1.1 (the "License"); you may not use this file except in 
*  compliance with the License. You may obtain a copy of the License at
*  http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
*  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
*  for the specific language governing rights and limitations under the
*  License.
*
* The Initial Developer of the Original Code is Xavier Franc - Axyana Software.
*
*/
using System;
using EvaluationException = System.Qizx.Api.EvaluationException;
using System.Qizx.XQuery;
using SingleBoolean = System.Qizx.XQuery.Dt.SingleBoolean;
namespace System.Qizx.XQuery.Op
{
	
	/// <summary> Implementation of operator 'castable as'.</summary>
	public class CastableExpr:CastExpr
	{
		public CastableExpr(Expression expr, XQType targetType):base(expr, targetType)
		{
		}
		
		public override void  Dump(ExprDisplay d)
		{
			d.header(this);
			d.property("type", targetType);
			d.child(expr);
		}
		
		public override Expression StaticCheck(ModuleContext context, int flags)
		{
			base.StaticCheck(context, flags);
			type = XQType.BOOLEAN;
			return this;
		}
		
		public override XQValue eval(Focus focus, EvalContext context)
		{
			context.at(this);
			return new SingleBoolean(evalAsBoolean(focus, context));
		}
		
		public override bool evalAsBoolean(Focus focus, EvalContext context)
		{
			XQValue v = expr.eval(focus, context);
			context.at(this);
			if (!v.Next())
				return isOptional;
			try
			{
				targetType.cast(v, context);
				return !v.Next(); // must be singleton
			}
			catch (EvaluationException e)
			{
				return false;
			}
		}
	}
}